Note: Descriptions are shown in the official language in which they were submitted.
sackground of the Inven-tion
1 Field of the Invention
The present invention pertains to systems for sensing
the angular position of a rotary shaft or other member. In
particular, tne invention pertains to a system associated with
such a rotary member and comprising an operator for producing
a programmed response in accordance with the angular position of
the rotary member. The invention finds application in many fields
including that of rotary valves. It may be used to indicate the
position of the rotary valve stem or the coaxial sha~t of an
ac~uator for the valve and thus the position of the attached
valve element whether it be open, closed, or in some intermediate
position. It can also be used to produce some other programmed
response to the valve stem, actuator shaft and/or valve element
position. For example, it may be associated with the valve
actuator so that the speed of rotation of the valve is control-ed
as a function of the position of the valve stem,actuator shaft
and/or valve element.
.
2. Brief Description of the Prior Art
One of the most common approaches in such systems
in the past has been to connect a potentiometer to the rotary
member whose angular position is to be sensed. The potentiometer
was, in some cases, directly mechanically connected to the rotary
member and, in other cases, indirectly mechanically connected to
the rotary member via a linkage of gears or the like. In either
case, the potentiometer would be driven by the rotary member and
would produce an output voltage proportional to the position of
the rotary member.
This approach has numerous disadvantages. One of these
is that the various parts, being mechanically connec-ted to one
another, are subject to wear and backlash leading to inaccuracy
in the position sensing particularly as the system ages. The
ff
~indings of the potentiometer are also subject to wear and this
can cause complete failure o the sensing apparatus. Furthermore,
such systems are quite expensive due to the mechanical complexity
and to the need to use high quality par,-s in an effort to combat
wear and backlash problems.
U. S. Patent No. 3,828,188 to Matula brie~ly describes
a prior art system in which a mirror rotates with a tension arm
and reflects greater or lesser amounts of light from an external
light source. This system appears to lack the precision and
versatility required in many of the applications of the present
invention. Furthermore, the system is adapted for relatively
light duty rotary machinery such as tape decks and would not be
suitable for use with apparatus such as valves and valve actuators
which are subjected to much more abuse.
U. S. Patents Nos. 3,767,992 and 3,770,965 to Edwards
et al. disclose somewhat more sophisticated systems in-which a
control device limits the amount of light either reflected from
-~ or transmitted across the control device. These systems also lack
the precision and versatility required in many applications. In
; 20 particular, they lack means for limiting the light reflected from
or transmitted across the control device to a relatively small
area so that small increments of movement of the control device`
can be detected. Additionally, the Edwards systems fail to -
provide adequate isolation of the light detection member from
light sources other than the control device. Neither the Matula ¦
nor the Edwards et al patents disclose any way of applying their
respective systems to rotary valves and actuators, one of the
primary environments of interest in the present invention.
Still another system is briefly disclosed in Machine
Design, Feb. 6, 1975. This system is based on light transmission
rather than light reflection. Thus it uses considerably more
space than is desirable and requires a separate member for the
control device rather than allor~ing it to be incorporated on or
in a rotary part already present in the rotary apparatus.
Furthermore, the system lacks versatility in that the con-
figuration of the light transmission limiting area is not
readily altered.
All of the above-described prior art systems have
disadvantages in terms of undue weight and expense.
Summary of the Invention .
In accordance with a particular embodiment of the
invention, there is provided, in combination with a rotary
member, a positional sensor-operator system comprising:
a light reflective program area carried by said rotary
member to rotate therewith, the length of said program area
extending in a circumferential direction with respect to said
rotary member and the width of said program area varying
along the length of said program area as a function of length-
wise distance from one end of said program area so as to be
indicative of the angular position of said rotary member and
the light reflective characteristics being substantially
uniform over said program area, a reference area having light
reflective characteristics substantially identical to those
of said program area and carried by said rotary member to
rotate therewith, the length of said reference area extending
- in a circumferential direction with respect to said rotary
member and the width of said reference area being substan-
tially uniform along its length, means for projecting light
onto at least a part of said program area over an extent
transverse to said program area at least as broad as the
maximum width of said program area and further operative to
project light onto at least a part of said reference area
over an extent transverse to`said reference area at least
as broad as the width of said reference area, primary
-- 4 --
.. . . ..
6~
detector means operative to detect the amount of light
being reflected from the entire width of a limited lengthwise
portion of said program area aligned with said primary detector
means, said primary detector means being disposed opposite
said program area whereby successive lengthwise portions of
said program area will pass and primary detector means as
said rotary member is rotated, said primary detector means
further being operative to produce an output signal which
is a function of the width of said program area; auxiliary
detector means disposed opposite said reference area and
operative to detect the amount of light being reflected
from a limited lengthwise portion of said reference area
aligned with said auxiliary detector means, said auxiliary
detector means further being operative to produce an output
signal which is proportional to the amount of light being
; reflected from the aligned portion of said reference area;
means for producing a net output signal which is a function
of the difference between the output signal of said primary
detector means and the output signal of said auxiliary detec-
tor means; and operator means operably connected to said
means for producing said net output signal to receive said
net output signal and produce a programmed response thereto.
The present invention comprises a positional
sensor and~or operator system comprising a light reflective
program area carried by the rotary member to rotate there-
with. The length of the program area extends in a circum-
ferential direction with respect to the rotary member, and
the width of the program area varies along its length as a
function of lengthwise distance from one end of the program
area. Thus the width of the program area at any given loca-
tion along its length is indicative of the angular position
- 4a -
of the rotary member. The system further comprises means
for projecting light onto at least a part of the program
area over an extent at least as broad as the maximum width
of the program area and primary detector means operative to
detect the amount of light being reflected from the entire
width of a limited lengthwise portion of the program area
aligned with the primary detector means. The primary
detector means is disposed opposite the program area whereby
successive lengthwise portions of the program area will pass
the primary detector means as the rotary member is rotated.
The primary detector means produces an output signal, e.g.
an electrical current or a voltage, which is a function of
the width of the program area, and this signal is received
by an operator means connected to the primary detector means,
The operator means is operative to produce a programmed
response to the output signal. For example, it may be used
to program the angular speed of the very rotary member whose
position is being sensed and/or to indicate its angular
position,
Although the invention is useful in connection
with many types of rotary members, it is particularly
applicable to rotary
- 4b -
~ r
valves and their actuators. The program area is preferably
provided on a film member which may be carried by the valve
stem (or a rigid coaxial extension thereof), the shaft of the
valve actuator or any other sui'able part rotating with the
valve element.
The primary detector means may be mounted in the same
housing with the light projecting means but sealed from direct
photo communication therewith. The primary detector means may
comprise a photocell or photomultiplier disposed in a chamber
in the housing facing a slit lying opposite and transverse to
the program area. The slit length is sized to admit light from
the entirety of the maximum width of the program area measured
in the direction of the slit. Alternatively, the primary detector
means may comprise a bundle of optical fibers with their ends
1~ forming an elongate array in the same general disposition with
respect to the program area as the above-mentioned slit. A
sensing device such as a photodiode is attached to the fibers
to sense the amount of light being carried by the fibers and
produce the output signal.
In either embodiment, there is precise control of the
light which reaches the primary detector means. The~system can
be designed so that the width of the slit or of the array of
iber ends is the limiting factor on the length of the lengthwise
portion of the program area from which light is reflected. This
limit can thus be made guite small so that very tiny increments
of angular movement of the rotary member can be detected. Also,
the slit or array of fiber ends is preferably located quite close
to the program area so'that extraneous light is effectively pre-
vented from reaching the primary detector means. Yet the rotary
3~ member and its program area are spaced slightly from the slit or
fiber array. Backlash and wear due to friction, mechanical inter-
connections, etc. are thus totally eliminated from the system.
The system may also be equipped with means to compensate
- for dulling of the reElective material of the program area and/or
the liqht projecting source. This may comprise a reflective
.referenCe area of the sam2 reflective material as the program
ea and generally paralleling the program area, but of sub-
stantially uniform width. The reference area is illuminated by
the same light projecting means as the program area, but a separate
auxiliary detector means is provided to sense the amount of light
being reflected from the reference area. Means are provided for
producing a net output signal which is a function of the dif-
ference between the output signals of the primary and auxiliary
1~ detector means. The operator means is directly responsive to the
net output signal and! thus, indirectly responsive to the output
signal of the primary detector means.
In the preferred embodiment, the program area is carried
by a film member, preferably having an adhesive backing, which
L~ may be placed directly on some rotary part of the apparatus
or on a special carrying member provided for the purpose. It
will be appreciated that the use of film has great advantages of
light weight and low cost. Furthermore, the film provides great
versatility in the system as the program is easily changed by
' either removing and replacing the film member or by covering one
film member and emplacing another.
Accordingly, it is a principle object of the present
invention to provide an improved means for producing a programmed
response to the an~ular position of a rotary member
Another object-of the invention is to provide a posi-
tional sensor-operator system which is especially adapted for use
with rotary valves and valve actuators.
Still another object of the present invention is to
provide a positional sensor-operator system which permits precise
detec-tion of very slight increments of movements of the associated
rotary member.
A further object of the invention is to provide a posi-
tional sensor-operator system which effectively eliminates light
from extraneous sourc~s from reaching th2 detection means.
- 6 - ~6~34
3'~
Still another object of the invention is to provide
positional sensor-operator system which is inexpensive,
lightweight, versatile, and conservative of space.
Aditional objects, features, and advantages of the
present invention will be made apparent by the following des-
cription of the preferred embodiments, the drawings, and the
claims.
Brief Descriotion of the Drawing
Fig. 1 is a diagrammatic representation of a system
according to the invention.
~ Fig. 2 is a perspective vie-~ of the light projection-
detection unit of the system of Fig. 1 with parts broken away.
Fig. 3 is a cross-sectional view of the light projection-
detection unit of Figs. 1 and 2 shot~n in relation to the program
carrying disc.
Fig. ~ is a plan view of a program carrying disc incor-
porating a second embodiment of the-invention.
Fig. 5 is a perspective vie~ of a rotary shaft, program .
carrying film and light projection-detection unit with means to
compensate for dulling of the program area or light projectlng
means.
Fig. 6 is a fragmentary view of a second form of detec-
tor means.
Fig. 7 is an elevational view of a film me~ber according
to the invention having a first program.
Fig. 8 is a graPh plotting speed against lengthwise
distance from one end of the prosram area for the program of Fig. 7
as a~plied to the rotation speed control system of Fig. 1.
Fig. 9 is a graph plotting angular posi-tion against time
for the program of Fig 7 as applied to the rotation speed control
sys-tem of Fig. 1.
Fig. 10 is an elevational view of a film member according
to the invention having a second program.
Fig. 11 is a graph similar to tha-t of Fig. 8 for the
-- 7
program of Fig. 10. ~ 6 ~
Fig. 12 is a graph similar to that of Fig. 9 for the
program of Fig. 10.
Description of the Preferred Embodiments
Referring now to Fig. 1 there is shown a system including
a rotary shaft 10 which rotates with a rotary valve element (not
shown) such as in a butterfly valve, ball valve, etc. Shaft 10
may be the valve stem or an extension thereof. Other rotary
members which rotate with the valve element such as a shaft or
journal in the valve actuator which engages and rotates with the
valve stem could also be used. A valve actuator diagrammatically
indicated at 12 serves to rotate the shaft 10 to open and close
the associated valve. In accord with the present invention there
is provided a program carrying disc 14 rigidly mounted on the
i shaft 10 to rotate therewith. Disc 14 has a radially directed
surface 14a and two axially directed surfaces one of which is
shown at 14b.
A film member 15 whose width is approximately the same .
as that of the radially directed surface 14a is applied to the
3 - surface 14a as by means of an adhesive backing on the rear face
of the film which lies adjacent the surface 14a. The front face
~f the film memb~r 15 has a program area 16 of light re~lective
material such as white paint, metal foil, etc. The program area
16 has a wide first end 16a, a pointed second end 16b, and side
; edges l6c which taper linearly from end 16a to end 16b (see Fig.
7). The remainder of the front face of the film member 15 comprises
two non-reflective areas 18 adjacent the side edges 16c of the
program area 16. Areas 18 may, for exam le, be flat black.
When the film member 15 is applled to the surface 14a
as shown in Fig. 1, the lengthwise dimension of program area 16 ex-
ten~s in a circumferential direction with respect to shaft l0 and
is indirectly carried by shaft 10 via the disc 14 and the attached
film member 15. The width of the program area 16, measured between
-- 8 --
the side edges 16c, varies as a linear function of lengthwise
~ ,tance from end 16a and as a difEerent linear function of length-
wise distance from end 16b. Lengthwise distance along program
area 16 from one end of the program area is proportional to
angular position with respect to that endi thus the width of the
program area 16 may be considered a linear function of either of
these two variables.
The varying width of program area 16 provides a program
for the control of an indicator opera-tor 22 and another operator
0 24. The program is transmitted to indicator 22 and operator 24
from a light pro~ection~detection unit ~0. As will be explained
more fully below, unit 20 projects light onto the program area
16 and detects the amount of light being reflected from the entire
width of a very small lengthwise portion of the progra~l area 16.
It will be appreciated that this amount of ,light will be propor-
tional to the average or mean width of the respective lengthwise
portion of the program area 16 and thus a linear function of the
length-~7ise distance of the portion from one end of the program area.
The unit 20 in turn produces an output signal which is a function
o~ the amount of light being detected. The signal is preferably
electrical. Although the output signal may be any function of the
amount of light being detected, it is for simplicity simply propor-
tional to the amount of light.
The output signal is transmitted from unit 20 to opera-
tor means 22 and 24 via suitable electrical connecting means such
as a cable 26. The circuit may include components for impedance
matching or electrical gain as required and as is well kno~7n in ;-'
the art. In the system shown, the signal is transmitted to two
different operator means although it could be transmitted to only
one or to more than two. Operator means 22 is an indicator having
a pointer movable around a dial or other sui-table means for-indi-
cating the angular position of shaft 10 and thus of the attached
valve element. The movement of the poi-nter is determined by the
output signal from uni-t 20. Operator 2~ is connected to the
~lve actuator 12 to vary the speed of the valve ac-tuator
and thus -the rotational speed of the shaLt 10 and attached valve
element. The speed variations effected by the operator 24 are
determined by the output signal from unit 20. It should be
understood that the two types of operators shown are only exem-
plary and that virtually any type of operator could be employed
in the system.
Referring now to Figs. 2 and 3, the unit 20 is shown
in greater detail and, for purposes of illustration, proportionately
larger with respect to disc 14 than in Fig. 1. Unit 20 comprises
a housing 28 forming two chambers 30 and 32. The two chambers
are sealed against direct photo communication with each other by
walls 34 and 36. Within chamber 32 is a light source such as
a light emitting diode 38. Other light sources such as filament
lamps can also be used although LED sources are preferred for
their reliability. A light diffusing screen 40 of ground glass,
glass bearing flashed opal, plastic or the like is disposed in
front of the diode 38 to form a part of the front of housing 28,
and particularly of that portion of the front of the housing which
defines the front of chamber 32. Power is provided to diode 38
via electrical leads 42 which pass through chamber 32 and cable
26 and thence to a suitable power source (not shown).
Wall 46 in part defines the front of chamber 30. Wall
46 has a narrow slit 44 therein. The length of the slit 44 is
great ènough to admit light from the entire width of the widest
part of program area 16. Since the slit 44 is preferably disposed
quite close to the program area, its length is preferably about
equal to the width of the widest part of the program area. Within
chamber 30 facing slit 44 is a light sensing device such as a
silicon photocell 48. A photomultiplier or other type of sensing
device could also be used. Photocell 48 is operative to detect
the amount of light entering slit 44 and produce an outpu-t signal
in the form of a variable voltage which is transmitted to the
34~
-- 1 o
operators by leads ~0 which pass through chamber 30 and cable
2~o
The front of the housing 28, generally comprised of
walls 36 and 46 and screen 40 faces the program area 16 o that
slit 44 lies transverse to the program area. For purposes of
illustrationj the unit 20 is sho~m as substantially spaced from
the disc 14 and film member. In ac-tual practice, it is preferable
to place the unit as close as possible to the program area so as
to exclude light from sources other than diode 38. The unit
0 should not, however, touch the program area as this would create
frictional wear. The diode 38, screen 40, and wall 36 comprise
a light projecting means for projecting light onto the part of
t~e program area aligned with the sllt 44. The housing 28,
including slit 44, and photocell 48 form primary detector means
for detecting the amount of light reflected from a limited
lengthwise portion of the program area and producing the output
signal.
Due to the thickness of wall 46, the slit 44 effectively
acts as a two slit system, particularly if the opposed side
0 surfaces of the slit are non-reflective. The break in the inner
surface of wall 46 formed by the slit 44 serves as one slit, and
the break in the outer surface of wall 46 formed by the slit 44
serves as the other slit. It will thus be appreciated that light
enters slit 44 from only that limited lengthwise portion of pro- ;-
gram area 16 which lies between lines 52 and 54. Similarly,
light from slit 44 strikes only that portion of photocell 48 which
lies between lines 52 and 54. Wall 36 is disposed at an angle
with respect to wall 46 so as to allow llght from diode 38 to
stri~e the furthermost part of program area 16 from which light
0 will enter the slit as indicated by the intersection of lines 52
and 56 on the program area. It will also be observed that the
width of photocell 48 is sufficient to receive light from the
entire area between lines 52 and 54. Thus the length of the
limited lengthwise portion of the program area from which reflecte~
~1~6~
ight is detected is limited only by the width of the sli-c 4~.
~ is noted that, just as the length of slit 44 is sufficient to
admit ligh~ from the entirety of the maximum width of program
area 16, i.e. at 16a, the screen 40 is long enough to illuminate
an extent, transverse to the program area at least as broad as
this maximum width. Similarly, the photocell 48 is long enough
to receive light from the maximum width. It will be appreciated
that the necessary dimensions for these various parts will depend
somewhat on the spacing of the parts from the program area and
from each other. The proper dimensions for given spacings can
be determined by well known means by one skilled in the art of
optics.
It has been noted that the length of slit 44 extends
in. a direction transverse to the program area 16. It is highly
preferable that the slit 44 lie in a direction perpendicular to
the lengthwise direction or direction of travel of the program
area. However, it will be appreciated that, for at least some
programs, the relative directions of the slit and program area
lengths may be transverse but not strictly perpendicular. However,
in either case, if the width of the program area is considered
as measured in the direction of the length of the slit, this
width will still be a function of mean lengthwise distance or
angular displacement from one end of the program area, and the
lengths of the slit, photocell, screen, etc. will always be suf- --
ficient to accommodate the maximu~ width of the program area
As mentioned above, the length o~ the limited lengthwise
portion of the program area from which light can be detected
at any given time is determined by the width of the slit 44. This
arrangement is much more convenient for accura-te control than
limiting the lengthwise por-tion by means of the photocell or the
light projecting means. The slit is preferably made as small as
is practical and placed as close as possible to the program area
so that the length of the limited length~ise portion will be q~lite
small. Thus very small increments of move~ent of the program
~rea can be detected by the detection means which makes for a
.lgh degree of precision in the system. The precision is also
enhanced by the use of the disc 14 of larger diameter than the
shaft 10 and the placement of the program area at the outermost
part OL the disc as this provides a given point on the program
area greater linear travel per degree of angular movement It will
be possible in some cases, where the shaft 10 is of sufficient
diame-ter or where less precision and more space conservation are
needed, to place the film member or other material defining the
program area directly on the shaft 10 as shown in Fig. 5.
The film member 15 of Figs. 1 and 7 is rectangular when
laid flat. In Fig. 4 there is shown another film m~mber 58
which provides the same program as film member 15 but which is
adapted to be placed on the axially facing surface 14b of the
disc 14. Film member 58 has a long arcuate side edge ~8a of
the same radius of curvature as the outer edge of surface 14b at
which edge 58a is disposed. The film member 58 also has a short -
arcuate side edge 58b parallel to edge 58a and ends 58c and 58d -;
~o which are aligne~ with radii of the disc 14. Film member 58 carries
a program area 60 whose length extends in a circumferential direc-
tion with respect to the shaft 10. Program area 60 has a wide end
60a coincident with end 58c of the film member, a pointed end ~ -
60b centered on end 58d of the film member, and side edges 60c
which taper from end 60a to end 60b so that the width of the pro-
gram area 60 is a linear function of either mean linear distance
from or angular displacement with rèspect to either of the program
area ends 60a and 60b. As shown, the program area 60 provides
exactly the same program as program area 16 of film member 15. The
0 light projection-detection unit used with the embodiment of Fig. 4
may be exactly the same as the unit 20 except that it will be disposed
with the front of the housing facing surface 14b rather than surface
14a of the disc 14 with the slit 44 transverse to the program area
60 and preferably aligned with a radius of the disc 14.
6~4
- 13 -
In Fig. 6 there is shown a portion of ano~her embodiment
' th~ invention in which the sLit 4~ and photocell 48 may be
replaced by a bundle of optical fibers 62 connected to a light
sensing device such as a silicon p-i-n photodiode 64 which sensRs
the amount of light carried by the fibers 62. The ends 62a of the
- fibers 62, referred to herein as sensor ends, are arranged in an
elongate array as shown. In use, the array of ends 62a faces the
program area in exactly the same way as the slit 44 of the embodi-
ment of Figs. 1-3. It will lie transverse to the program area
and preferably at a right ang~e to the direction of movement of
the program area. The a~ray must be long enough to receive light
from the entire width of the widest part (measured in the direc-
tion of the arra~) of the program area. The width of the array
will determine the length of the limited lengthwise portion of
the program area from which light can be received at any one time.
Photodiode 64 is operative to produce the appropriate output sig-
nal in the form of a varia~le current and has leads 66 for trans-
mitting this signal to the operators.
The apparatus of Fig. 6 may be placed ln a housing with
~ the ends 62a disposed in a slit in order to protect the apparatus
; from physical damage, dust, dampness, etc. and to help maintain the
configuration of the array of ends 62a. However, this expedient
-~ is not necessary to isolate the apparatus from direct photo-com-
mu~ication with the light source since only light rays striking
the ends 62a will be carried by the fibers. Similarly, the
photodiode 64 is only responsive -to light being carried by the
fibers. It is desirable, however, to provide some means for fixing
the apparatus of Fig. 6 with respect to the light projecting means~
Otherwise, the remaining parts of the system, e.g film member,
3 light projecting means, operators, etc., can be identical to those
of Figs. 1-3.
It will readily be appreciated that all the functions of
the light projection-de-tection unit may be carried out electrically
so that there need be no moving ?ar~s in the unit 20. The program`
3~
area does move relative to the uni-t 20 but does not touch it.
Thus, mechanical wear is eliminated from these parts of the
~stem. Furthermore, the use of a film element of negligible
volume and weight and of electrical components makes this entire
part of the system small, compact, and lightweight
There is, however, a possibility of dulling of the
reflect-ve material of the program area and/or the light source,
particularly if the latter is a filament lamp rather than the
preferred LED source. Fig. 5 depicts a modified form of the
invention which compensates for such dulling. The modification
includes the shaft 10. A film member 68 is attached directly to
the radially facing surface of shaft 10 and its outer surface
comprises two generally parallel reflective areas 70 and
72 whose lengths extend in a circumferential direction with
~5 respect to the shaft 10. Area 70 is a program area substantially
identical to program area 16 of Figs. 1 and 7. Area 72 is a
reference area of substantially constant width, preferably equal -;-
to the maximum width of area 70, and comprised of the same reflec-
tive material as area 70.
~0 The modification also includes a light projection-detection
unit 20' having a two-chamber housing 28'. In one cha~ber of the
housing 28' is a light source (now shown~ located behind a dif-
fusing screen 40' at the front of the housing~ The unit 20',
as thus far described, is identical to unit 20 of Figs. 1-3.
Unit 20' differs from unit 20 in that the other chamber contains
not one but two slits 74 and 76 aligned end-to-end each of which
~aces a respective one of the reflective areas 70 and 72. The
slits are of identical size and each one lies transverse to its
respective reflective area, preferably at right angles to the - -
direction of motion of the areas. Behind each of the slits 74 an~
76 lies a respective photocell 78 or 80 similar to photocell
- 48 of Figs. 2 and 3. Photocells 78 and 80 are identical and cali-
bratedand each is operative to detect the amount of light entering
ts respective slit and produce a propo.tional output signal.
- 15 -
Respective leads 82 and 84 transmit the two output signals to an
e]ectronic device ~6 which produces a net output signal which is
p ~ortional to the difference be-tween the output signals of the
two photocells 78 and 80. The primary detector means of the
modified sys-tem co~prises photocell 78 and slit 74. The auxiliary
detector means of the modified system comprises photocell 80
and slit 76. The net output signal produced by device 86 is trans-
mitted by leads 88 via cable 26 to the operators 22 and 24 which
are thus directly responsive to the net output signal and indi-
rectly responsive to the output signal of the primary detector
means. It will be appreciated that the net output signal compen-
sa-tes for any dulling--by taking the difference between the output
signal resulting from the program area and the output signal re-
sulting from the reference area. Since both areas 70 and 72 are
comprised of the same material, they will fade at the same rate,
and since they are both illuminated by the same light source,
any dulling of the latter will be nullified by the use of the
reference area.
Referring now to Figs. 7-12, several different types of
programs and the ways in which they might be applied to the system
of Fig. 1 are illustrated. Fig. 7 shows the above-described
film-member 15 in which the width of the program area 16 varies
linearly with distance from end 16a. More particularly, the
width of the program area 16 is proportional to the distance from
end 16a so that w = -ax; where w = width, x = distance from end
16a, and a is a negative constant. The negative of a is used since
the width w decreases from end 16a to 16b.
At this point it should be noted that in referring to
characteristics of the limited lengthwise portions of the program
area such as width, linear distance from one end of the program
area, angular displacement with respect to one end of the program
area, etc , it is actually the mean width, mean distance, etc
that is meant since the limited leng-thwise portions do have some
length~ise dimension. However, this lengthwise dimension in the
- 16 -
preferred embodiments is so small that the various values men-
t. ~~~ed above will often be referred to herein simply as the
width, distance, ang~llar displacement, etc. The light sensing
device of the primary detector means of the system, i.e. photocell,
photomultiplier, photodiode or the li~e, can be devised so that
its output signal is any desired ~unction of the mean width of the
limited lengthwise portion of the program area from which light
is being detected. Preferably the output signal is proportional
to the width, and, for simplicity, we will assume here tha-t.the
-O output signal is equal to the width. The speed of the valve
actuator 12 may be controlled as any desired function of the output
- signal. Again, the function is preferably a simple proportion and,
for simplicity, we will assume that the constant.of proportionality
is l so that the speed s of the valve actuator is equal to the
5 width _ of the program area. Then as shown by the solid line p
in Fig. 9, the speed of the actuator is a decreasing linear func-
tion of the mean distance of the limited lengthwise portion of the
program,from which light is then being detected,from end 16a. Line
~ has the equation s = -ax. It will also be appreciated that,
since the program area remains at a constant distance from the axis
of rotation, linear distance from one end of the program area is
proportional to angular displacement with respect to that end of
the program.area. Thus, it may also be said that s = -ar e ;
where r - distance from the axis, and e = angular displacement
from the end of the program area from which x is measured.
In many instances, it is desirable to regulate a valve
actuator's speed so that the valve element is rotated at a relatively
fast rate at and near its open position where the fluid it controls
offers little resistance and at a relatively slow rate at and near
its closed position where there is more resistance.- This objective
can be achieved with the program of area.16. For example, the
length of the program area could be made equal to one fourth the
circumference of the shaft, disc, or other rotary member on which
the ~ilm is to be carried. l'he film would be positioned on the
rotary member so tha-t wide end 16a would be aligned with the slit
~ of the detec-Lion means when the valve is in its op2~ position
and the pointed end 16b would be aligned ~ith the slit 44 when
the valve is in its closed position Then as the valve element
mPved from its open position to its closed position, its speed
would decrease according to the equation for line p. The rate OL
speed decrease could b;e determined as desired by selecting an
appropriate constant of proportionality a between the width of
the program area and distance from end 16a, the constant -a also
representing the slope of the line p and thus the rate of decrease
; in speed per unit of~linear movement of the program area. If an
indicator such as 22 is used in the system, its movement ~ may be
.
controlled by the same function, i.e. ~ = -ax.
It will be appreciated that, for the arrangement described
above, the value of x is increasing as the valve is ratated-from
its open position to its closed position. Upon reverse rotation,
;. .
~.~ the value of x will be decreasing, but the line ~ will still
, .
describe the speed s as a function of x so that the actuator
wlll still be moving faster near the open position of the valve
and slower near the closed position. It will also be appreciated
that the opposite effect could be achieved by placing the film
member so that the pointed end 16b is aligned with the slit 44 when
the valve is in its open position and the wide end 16a is aligned
~5 with the slit 44 when the valve is in its closed position.
As explained above, the variable x, representing the dis-
tance from end 16a of the limited lengthwise portion aligned with
slit 44 determines the output signal of the primary detection means.
~owever, since this output signal is transmitted back to the valve
; actuator to control its speed and thus that of the connected pro-
gram area, the value of x as a function of time is controlled by
this output signal. Fig. 9 shows the way in which x varies with
time for the arrangement described with respect to Fig. 7. It
will be appreciated -that the speed s of the valve actuator is also
3g~
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the speed of the valve element and connected rotary part on
wi~:~h the program area is carried. The speed s can be written
as dx/dt where t = time. Then, from the equation for s we can
write dx~dt - -ax. This latter equation is solved as follows:
dx/dt = -ax
dx/x = -a dt
; ln x = -at
,, x = eat
This solution is shown graphically by the curve m in
Flg. 9 for the time period in which the valve moves from its open
to its closed position.
It can be seen that _ changes rapidly for the smaller
values of t but very rapidly for greater values of t.
Turning to Figs. 10-12 there is shown a film member 88
~5 having a reflective program area 90 on its forward face. The
program area 90 has ends 90a and 90b corresponding to the ends
of the film member 88. From end 90a to line xi, whose distance
from end 90a is also equal to a given value denoted by xl, the
~ width of the reflective program area is a constant cl equal to
;0 the width of the film member 88. From line xl to line x2, whose
distance from end 90a is also equal to a given value denoted by
x2, the width of the~program area is a constant c2 less`than the
width of the film member 88. In this area, the program area has
side edges 90c spaced inwardly from the sides of the film me~ber,
and adjacent the slde edges 90c are non-reflective areas 92. From
line x2 to end 90b, the width of the program area 90 is again the
constant cl equal to the width of the film member 88.
- Fig. 11 graphically illustrates the way in which the speed
s of the valve actuator is controlled by the progr~m of the film -
member 88. Again we will assume for simplici-ty that the speed
of the actuator is equal to the width w of the program area Then
w = s = cl for 0 ~ x C xl and x2~ x ~ xmax
w = s = c2 for xlc x C x2
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~he way in which this speed function would apply to the various
itions o~ the valve element would depend on which parts of
the program area 90 are aligned with the slit ~4 when the valve
element is in these various positions~ Fig. 12 illustrates the
movement of the program area, or any given point thereon, as a
function of time. The graph of Fig. 12 comprises a continuous
curve including three linear segments nl, n2, and n3. Over the
segment nl, x increases relatively rapidly with time from 0 to xL
at a constant rate represented by the slope of segment nl. Over
segment n2 x increases more slowly from xl to x2 at a constant
bu. lesser rate. Over the segmen-t n3, x again increases rapidly
with time from x2 to the maximum value of x'at the same rate as in
_
; segment nl.
~; It ~ill be appreciated that the embodiments of Figs. 7-9
and Figs. 10-12 are only exemplary an~ that numerous other embo-
diments could be provided by varying the configuration of the
program area and/or varying the placement of the program area
with respect to the various positions of the valve element. Addi-
tionally, the output signal of the primary detector means, the
width of the program area and the speed of the valve actuator
have all been assumed to be equal in the above examples. However~
it will be appreciated that the electrical components of the
system could be devised so that the output signal of the primary
detector means is any desired function of the width of the program
area and the speed of~the valve actuator is any desired function
of the output signal. This type of variation offers even more
possibilities for varying the responses to various programs. In
particular, it is noted that the actuator speed can be controlled
as various functions of either the width of the program area or the
output signal of the primary detection means such as parabolic func-
tions, logarithmic functions, etc. The movement of the program
area with respect to time can be similarly determined by suitable
functions bui~t into the system in a manner well known to those
skilled in the art
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It will readily be appreciated tha-t the preferred embo-
di nts of the invention described above provide n~merous advan-
tages. They are free from mechanical wear, backlash, etc. A
high degree of precision and accuracy is provided, particularly
when the limiting width of the slit or array of fiber ends is
quite small~ The systems as shwon are perfect for applications
involving valves and valve actuators but are also well suited
for many other applications. Great versatility is provided by
the use of a reflective program area, particularly if it is
carried by a removable adhesive film member. The use of such
film members also makes the system inexpensive, light weight, and~
conservative of space.
Many modifications of the preferred embodiments described
above are possible without departing from the spirit of the inven-
tion. It is thus intended that the scope of the invention be
lim}ted only by the claims which follow.
' j
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