Electrostatic-type registration system

A non-contact type registration system employing dipole-type electrostatic charges for precisely positioning insulative material to a selected location or workstation.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to non-contact means for moving insulative 
material to a selected location, in general, and to an electrostatic 
charge-controlled material positioning system for precisely positioning 
such material to an assembly machine workstation, in particular. 
2. Description of the Prior Art 
Various types of intermittent motion machines are presently available for 
registration purposes or for positioning portions of a web or individual 
pieces of material to a selected location or assembly machine workstation 
with varying degrees of precision. The means for determining when material 
has been properly positioned to a particular location in these types of 
machines may be conveniently thought of as falling into either one of two 
general categories. In one category, physical contact is made between the 
material to be positioned and the sensing means that determines when the 
material is positioned to a selected location. In the other category, a 
material-position determining sensor would sense material position without 
making physical contact with the material. 
In intermittent motion machines incorporating the contact-type sensor 
mentioned above, the shape of material to be positioned normally is 
permanently altered in order for it to properly cooperate with the 
position determining sensor that senses when the material has been 
positioned to a selected location. Such alterations increase costs in that 
means must be provided to produce such alterations, and very often more 
material is required either because of the altered portion of the material 
being unsuitable for other uses, or having to provide additional materials 
so that it can be altered for subsequent cooperation with a contact-type 
material position sensor. 
Prior art intermittent motion machines of the non-contact type usually rely 
on substances being applied to the material to be positioned in order to 
indicate actual material position. In U.S. Pat. No. 3,977,586 to HERTRICH, 
for example, light reflecting surfaces are added to the material to be 
positioned. As suggested in the HERTRICH patent, magnetic material could 
also be added to the material to be positioned and a magnetic sensor would 
then be employed to determine when the material had been positioned to the 
desired location. The addition of such substances to the material to be 
positioned would also add to overall costs both for providing the 
substance to be added and for placing it on the material. In addition, 
that portion of the material on which the substances are deposited may not 
be available for use in the finished end product which would reduce 
material yields and thereby increase material costs. 
A primary object of the resent invention is to provide apparatus for 
determining the position of a portion of an insulative material with 
respect to a selected reference frame or position. 
Another object of the present invention is to provide material position 
determining apparatus that does not physically contact the material for 
material position-determining purposes. 
A further object of the present invention is to provide material 
positioning apparatus that will not produce permanent physical alterations 
in the material to be positioned. 
Other objects, features and advantages of the present invention will be 
readily apparent from the following detailed description of a preferred 
embodiment thereof when taken in conjunction with the accompanying 
drawings. 
SUMMARY OF THE INVENTION 
In accordance with the teachings of the present invention, a non-contact 
type electrostatic registration control system for precisely positioning 
insulative material to a selected location or assembly machine workstation 
is disclosed. The system includes apparatus for placing a localized 
dipole-type electrostatic charges on the material to be positioned. Means 
are provided for sequentially driving electrostatically charged material 
or portions of such material to said selected location or workstation in 
accordance with signals derived from said dipole-type electrostatic 
charges.

BRIEF DESCRIPTION OF A PREFERRED EMBODIMENT 
Turning now to the drawings, in FIG. 1A, a schematic diagram of film 
assembly machine 10 incorporating a preferred embodiment of the insulative 
material 12 registration or positioning system of the present invention, 
is depicted. In FIG. 1A, insulative material 12 is in the form of a 
polyester, teflon, etc., web 4 to 5 mils thick that was previously wound 
into roll 14 and then placed on rotatably mounted unwind mandrel 16, in a 
conventional manner. The free end of web 12 was attached to roll 18 which, 
in turn, was mounted, in a conventional manner, on rotatably mounted 
rewind mandrel 20. Insulative web 12 is driven from roll 14 onto roll 18 
by drive means 22 and 24 which are mechanically coupled to rolls 14 and 18 
through paths 26 and 28, respectively. 
The registration control or material positioning system of the present 
invention includes a plurality of distinct functional parts that cooperate 
with one another to provide the ultimate material-positioning function. 
Each of these functional parts will be described as well as the manner in 
which they cooperate or interact with other functional parts to provide 
precise insulative material positioning. 
Uniformly spaced dipole-type electrostatic charges are placed on web 12 as 
it is intermittently moved between electrically conductive electrode 30 
and an electrically conductive reference surface in the form of rotatably 
mounted, electrically conductive cylindrical roller 32 by drive means 22, 
24. Electrode 30 is connected to the positive output terminal of pulsed 
power supply 34 through a path 36 and cylindrical roller 32 is connected 
to the negative and grounded output terminal of the power supply 34 
through a path 38. The input to power supply 34 is connected to a suitable 
source of electrical energy (not shown) through input terminals 40 and 42. 
Power supply 34 is pulsed or gated on and off by a control signal from 
control means 44 through path 46. Other components of the insulative 
material positioning system of the present invention, including drive 
means 22, 24, are also responsive to signals derived by said control means 
44. 
Workstation 48 performs a particular film assembly operation such as 
cutting, attaching material, etc., on a portion of insulative material or 
web 12 after the web portion has been moved into the workstation 48 by the 
drive means 22, 24. As mentioned above, drive means 22, 24 are responsive 
to signals derived by control means 44. Control means 44 derives such 
signals in response to various input signals form various assembly machine 
10 sensors. With respect to the operation of the positioning of a portion 
of web 12 within workstation 48, electrostatic charge-sensing probe 50 is 
positioned on machine 10 over and in relatively close proximity to one 
edge of web 12 such that it is capable of sensing the dipole charges 
placed on the web 12 by electrode 30. Probe 50 is shown positioned 
downstream of workstation 48 in the direction of web 12 movement but could 
be located upstream of or within the workstation 48. When probe 50 senses 
a charge on web 12, it generates a signal representative of the presence 
of such a charge which is then routed to control means 44 through path 52. 
Upon receiving a signal from probe 50, control means 44 transmits a drive 
termination signal from probe 50, control means 44 transmits a drive 
termination signal to drive means 22, 24 through paths 54, 56, 
respectively, causing drive means 22, 24 to stop a particular portion of 
web 12 within workstation 48, a portion of web 12 that is directly related 
to the physical distance between electrostatic charge-sensing probe 50 and 
the workstation 48. 
After control means 44 transmits a stop signal to drive means 22, 24 
through paths 54, 56 respectively, the control means 44 transmits an 
enable signal to workstation 48 through path 58 which causes workstation 
48 to initiate a particular film assembly operation on web 12. At the same 
time that workstation 48 is enabled to perform an operation on web 12, 
control means 44 transmits on/off or gating pulse 60 to power supply 34 
through path 46. Referring additionally to FIG. 1B, gating signal 60 
causes power supply 34 to momentarily apply an approximately 1,500 VDC 
potential between electrode 30 and reference surface 32. The end of 
electrode 30 is in the form of a 25 mil diameter stainless steel needle 62 
whose free end has an extremely small radius of curvature (approaches 
zero), has the free end spaced approximately 3-15 mils from web 12. The 
application of 1,500 VDC between electrode 30 and reference surface 32 
produces a relatively intense electrostatic field between these two 
electrodes. With an edge of web 12 being positioned between needle 62 and 
reference surface 32 and with 1,500 VDC being established by power supply 
34 between needle 62 and reference surface 32, a relatively small area of 
about 4 to 5 mil of the web 12 will acquire a dipole-type electrostatic 
charge of approximately 1,000 V. A dipole-type charge is one of long 
duration and, therefore, its charge level will not change over extremely 
long (months) periods of time. 
The voltage applied between the electrode 30 and the reference surface 32 
which produces the relatively intense electrostatic field therebetween 
must be less than a magnitude required to produce a corona. A corona may 
generate visible light of sufficient magnitude to be harmful to the 
material to which a dipole-type charge is to be applied, or generate ozone 
which may be objectional to personnel in the vicinity thereof. If, for 
example, the material is photosensitive film, the visible light may cause 
premature film exposure (fogging) and thereby render such material 
worthless. A corona is defined herein as the ionization potential or 
voltage at which ions acquire enough energy to leave the electrode 30 and 
thereby cause visible light to be generated in the vicinity thereof. The 
theoretical ionization potential for most electrical conductors under 
normal atmospheric conditions including normal temperature and pressure is 
approximately 4600 VDC. The 1500 VDC applied herein between the electrodes 
30 and 32 is well below this magnitude and does not produce visible light. 
When workstation 48 has completed its assembly operation on that portion of 
web 12 that is associated with the dipole charge on web 12 that cause 
control means to generate signals controlling drive means 22, 24, 
workstation 48 and power supply 34, the workstation 48 transmits a signal 
to control means 44 through path 64 indicating to the control means 44 
that another portion of the web 12 should be moved into workstation 48 so 
that an assembly operation can be performed on this other web portion. 
When control means 44 receives this sequence initiating signal from 
workstation 48 through path 64, control means 44 transmits drive signals 
to drive means 22, 24 through paths 54, 56, respectively, causing the 
drive means 22, 24 to move an additional portion of web 12 into 
workstation 48 as determined by the dipole-type charge associated with the 
additional web 12 portion that is sensed by electrostatic charge sensing 
probe 50. This type of movement of discrete portions of web 12 into 
workstation 48 is repeated for all subsequent portion of insulative web 12 
on which the same assembly operation is to be performed on web 12 by the 
workstation 48. 
In a web-handling assembly machine such as machine 10 shown in FIG. 1A, it 
is sometimes difficult to either physically align or to maintain the 
alignment between charge-sensing probe 50 and the relatively smallarea 
dipole-type spaced-apart electrostatic charges located along one edge of a 
web of insulative material as the web moves toward the probe 50. If such 
alignment problems should occur, they can be overcome by changing the 
shape of the electrode employed to place a dipole-type charge on the 
insulative web. With reference to FIGS. 1A, 1B and 1C, if needle end 62 of 
electrode 30 of machine 10 in FIGS. 1A and 1B is replaced by an 
electrically conductive stainless steel blade such as blade 66 in FIG. 1C, 
the dipole-type electrostatically charged area produced on the web by the 
blade 66 will be in the form of a straight line that is preferably 
oriented at right angles to an edge of the web 12. A schematic diagram of 
the spaced-apart dipole-type electrostatically charged areas that would 
appear along one edge of web 12 if the electrode employed to produce such 
a charge terminated in needle 62 as shown in FIGS. 1A and 1B are shown in 
FIG. 2 as circular spots 68. Whereas the spaced-apart dipole-type 
electrostatically charged areas that would appear along another portion of 
one edge of web 12 if the electrode employed to produce such a charge 
terminated in thin blade 66 as shown in FIG. 1C is shown in FIG. 3 as 
narrow lines 70. By employing blade 66 in machine 10 as the termination of 
electrode 30 to produce narrow line dipole-type charged areas in web 12, 
considerable lateral movement of charge-sensing probe 50 with respect to 
web 12 can be tolerated before the precise positioning of various portions 
of web 12 into work station 48 is adversely affected. 
In assembly machine 10 reference position generating dipole-type 
electrostatic charges are placed on moving web 12 in the machine 10 a 
short time before they are sensed by charge-sensing probe 50 for web 12 to 
workstation 48 positioning or registration purposes. As noted above, the 
magnitude of a dipole-type charge in an insulative web will remain fairly 
constant for very long periods of time. Depending upon the type of 
insulative material involved, it is not unusual for dipole-type 
electrostatic charges to retain their charge magnitude over a period of 
several months. In light of this fact, an alternate preferred embodiment 
of the present invention would be to place dipole-type electrostatic 
charges on an insulative web in a separate web charging operation long 
before the web is placed in a machine for assembly purposes, and then 
store the charged web for an extended period of time before the web is 
utilized. Web charging machine 68 schematically illustrated in FIG. 4 is a 
machine whose sole function is to place spaced-apart, reference position 
generating, dipole-type charges on a web of insulative material. 
Referring now to FIG. 4, in charging machine 68 insulative material 70 in 
the form of a polyester teflon, etc., web 5 mils thick was previously 
wound into roll 72 and then placed on rotatably mounted unwind mandrel 74, 
in a conventional manner. The free end of web 70 was attached to roll 76 
which, in turn, was also mounted in a conventional manner on rotatably 
mounted rewind mandrel 78. Insulative web 70 is driven from roll 72 onto 
roll 76 by drive means 80 and 82 which are mechanically coupled to the 
rolls 72, 76 through path 84, 86, respectively, in response to drive 
signals from control means 87. 
Spaced-apart, dipole-type electrostatic charges are placed on web 70 as it 
is moved between electrically conductive electrode 88 and an electrically 
conductive reference surface in the form of rotatably mounted, 
electrically conductive cylindrical roller 90 by the drive means 80, 82. 
Electrode 88 is connected to the positive output terminal of pulsed power 
supply 92 through path 94 and cylindrical roller 90 is connected to the 
negative and grounded output terminal of said power supply 92 through path 
96. The input to power supply 92 is connected to a suitable source of 
electrical power (not shown) through input terminals 98 and 100. The 
charging of web 70 is initiated shortly after control means 87 transmits 
drive signals to drive means 80, 82 through paths 102 and 10, 
respectively. After drive signals have been transmitted to drive means 80, 
82, power supply 92 is pulsed or gated on and off by gating pulses 106 
from control means 87 through path 108. Gating pulses 106 cause power 
supply 92 to apply a DC potential between electrode 88 and reference 
surface 90 in the form of a train of 1,500 VDC voltage pulses. This 1,500 
VDC potential between electrode 88 and reference surface 90 produces an 
extremely intense electrostatic field between electrode 88 and surface 90 
and a series of spaced-apart dipole-type charges along one edge of moving 
web 70 whose spacing is determined by the rate of web 70 movement and the 
rate at which power supply 70 is being gated by control means 87. The end 
of electrode 88 terminates in stainless steel needle 110 having the same 
physical dimensions as needle 62 shown in drawing FIGS. 1A and 1B. 
Inasmuch as dipole-type charges are applied to web 70 while the web 70 is 
in motion, this tends to lengthen or enlarge the physical size of the 
charged areas. This is so whether electrode 88 has a needle end as shown 
in FIG. 4 or terminates in a blade as shown in drawing FIG. 1C. A 
needle-ended electrode would produce elongated charged areas 112 if the 
web charging apparatus of FIG. 4 was employed which, for the sake of 
convenience only are shown (dashed) on web 12 in drawing FIG. 2. A 
blade-ended electrode would produce charged areas 114 which, for the sake 
of convenience, are shown (shaded) on web 12 in drawing FIG. 3. Elongated 
or enlarged charged areas would normally introduce alignment or 
registration errors into the web registration or positioning system of the 
present invention. However, electrostatic probes are presently available 
for use as, for example, probe 50 in assembly machine 10 shown in FIG. 1A 
that can look at a very narrow slice or portion of the dipole-charged area 
on web 12 which would all but eliminate the errors that would otherwise be 
produced by such charged area enlargement. As shown in FIG. 5, this 
presently available electrostatic probe could look at a relatively narrow 
slice of a charged area that is represented by probe voltage curve 116, 
between, for example, lower limit 118 of curve 116 and upper limit 120. 
Instead of positioning a portion of an insulative web to a particular 
location or workstation for web assembly purposes, the inventive concept 
of the present invention may also be employed to position articles or 
discrete pieces of insulative sheets of material to a particular 
workstation. A dipole-type electrostatic charge may be applied to a 
specific location or area on the discrete piece of insulative material or 
reference frame and this charged area would serve as the reference point 
for reference frame or insulative material positioning. Apparatus for 
placing a dipole-type electrostatic charge on articles or individual 
pieces of insulative material to establish a reference point for material 
positioning purposes is schematically shown in drawing FIGS. 6A and 6B. In 
FIG. 6A, movably mounted belt 122 has a plurality of spaced-apart material 
locating fixture pairs 124A and 124B, 126A and 126B, 128A and 128B, etc., 
having the same size and shape, that are fixedly attached to the movably 
mounted belt. Fixtures 124A,B, 126A,B, and 128A,B have individual articles 
or pieces or insulative material 130, 132 and 134 located within the 
fixtures, respectively. Control means 136 causes conventional indexing 
type drive means (not shown) similar to that employed in machines 10 and 
68 in FIGS. 1A and 4, respectively, to sequentially move individual pieces 
of insulative material 130, 132, 134, etc., to the same specific location 
between electrode 138 and rotatably mounted electrically conductive 
reference surface 140. The positive output terminal of power supply 142 is 
connected to electrode 138 through path 144 and the negative and grounded 
output terminal of power supply 142 is connected to reference surface 140 
through path 146. Power supply 142 is connected to a suitable source of 
electrical energy through terminals 148 and 150. After control means 136 
has caused its associated drive means to position insulative material 132 
to a specific location between electrode 138 and reference surface 140 as 
determined by a material positioning signal from the associated drive 
means to control means 136 on path 151, the control means 136 transmits 
pulse 152 to the power supply 142 through path 154, causing the power 
supply 142 to apply a DC potential between electrode 138 and reference 
surface 140 in the form of a 1,500 VDC voltage pulse. The voltage pulse 
momentarily causes power supply 142 to produce an intense electrostatic 
field between electrode 138 and reference surface 140 and because 
electrode 138 terminates in stainless steel needle 156, circular shaped 
dipole-charge 158 (FIG. 6B) is established in insulative material 132 by 
the electrostatic field. 
Control means 136 and its associated conventional drive mans positions all 
fixtures on support belt 122 together with individual pieces of insulative 
material to the same specific location between electrode 138 and surface 
140. Fixture 124A,B and insulative material 130 have previously been 
positioned to the specific location whereat circular shaped dipole charge 
160 was applied to the material 130. Fixture 128A,B and insulative 
material 134 supported therein will be moved into the specific location 
after the drive means (not shown) associated with control means 136 has 
moved fixture 126A,B and insulative material 132 away from the location 
between electrode 138 and surface 140 where dipole-type charge 158 was 
applied to the insulative material 132. 
If it is important that insulative sheets of material 130, 132, etc., not 
rotate about an axis that is perpendicular to the sheets of material, an 
additional charged area 162, 164, etc. could be placed on the insulative 
sheets 130, 132, etc., respectively, by electrodes 168 and 170 (shown 
dashed in drawing FIG. 6A), the electrodes being electrically connected to 
electrodes 138 and 140, respectively. This pair of charged areas could be 
sensed by a pair of electrostatic charge sensors mounted in a specific 
known location, a pair that could, for example, include sensors 50 and 122 
which are shown for convenience only in drawing FIG. 1A. In FIG. 1A, the 
output of probe or charge sensor 50 could be combined with the output of 
probe or electrostatic sensor 122 (shown dashed) by means of AND gate 174 
(also shown dashed). If a two probe arrangement were employed in, for 
example, a machine such as assembly machine 10 in drawing FIG. 1A, control 
means 44 would respond for control purposes only when probes 50 and 122 
were sensing separate spaced-apart electrostatic charges on web 12 or on 
individual sheets of insulative material such as the sheets of material 
depicted in drawing FIGS. 6A and 6B. 
DISCUSSION 
The insulative material registration or positioning system of the present 
invention is one that does not rely on physical contact with or permanent 
alteration of the material to be positioned, in order to precisely 
position the material to a particular location. The extremely long 
duration dipole-type electrostatic charge placed on the insulative 
material by, for example, electrode 30 in assembly machine 10 that is 
schematically illustrated in FIG. 1A, primarily results from the alignment 
or orientation of molecules in portions of the insulative material when it 
is subjected to a fairly intense electrostatic field such as that 
periodically established between the electrode 30 and reference surface 22 
in the assembly machine 10. As mentioned above, the preferred magnitude of 
this dipole-type long duration charge is 1,000 V which results when a 
voltage of 1,500 VDC is established between the electrode 30 and reference 
surface 32 for a 5 mil polyester teflon, etc., web. Sensing probe 50 on 
machine 10 in drawing FIG. 1A, which is physically spaced from web 12, can 
adequately sense a particular charged area of this magnitude on the web 
without having to make web contact. 
The positioning system of the present invention can position insulative 
materials that are capable of retaining an electrostatic charge for finite 
periods of time. Included within the definition of insulative materials 
are both dielectric and semiconductive materials. While many 
semiconductive materials can maintain an initial charge level for a 
reasonable length of time, the present invention can be more effectively 
utilized for the positioning of dielectric materials which can readily 
hold their initial dipole-type electrostatic charge for many months. 
It will be apparent to those skilled in the art from the foregoing 
description of my invention that various improvements and modifications 
can be made in it without departing from its true scope. The embodiments 
described herein are merely illustrative and should not be viewed as the 
only embodiments that might encompass my invention.